18 



ing soon to brown. The liquid is red, and after addition of ammonia (dilute) changes 

 to violet blue. 



(2) Alcohol from ammonia solution. Amyl alcohol uncolored. On adding water 

 and a few drops of hydrochloric acid no color should develop. The liquid is brown 

 and becomes red on addition of hydrochloric acid. 



If the wine gives these reactions, then no coal-tar colors are present. 



Cazeneuve's test 



For the detection of coal-tar dyes containing the sulpho-group (acid fuchsin, etc.), 

 azo colors, Bordeaux red, ponceaus, congo, etc., 0.2 gram of mercuric oxid is added 

 to 10 cc of wine in a test glass and shaken vigorously for about half a minute, heated 

 to boiling, and passed through a double filter paper. If the coal-tar colors are present, 

 the filtrate will be colored red. Wines containing a large amount of tannin some- 

 times give a light-gray color. Red oxid of mercury can not be used for this purpose. 

 Some very dark genuine red wines & (from .Trollinger and Portuguese grapes) will 

 give a red filtrate under these conditions. 



In most natural red wines, however, under these conditions the red color is 

 destroyed. 



Falieres-Ritter test. c 



One hundred cc of wine are made alkaline with 5 cc of ammonia and shaken vig- 

 orously with 30 cc of ether in a suitable retainer. With a pipette remove 25 cc of the 

 ethereal layer (filtration is not allowable as the filter paper retains fuchsin) and 

 evaporate in a white porcelain dish with addition of acetic acid and a strand of white 

 wool. After evaporation of the ether the wool will be dyed d if coal-tar colors are 

 present and remain white in the absence of such colors. 



c. EXAMINATION FOR FOREIGN VEGETABLE COLORS. 



No reliable method can at present be given for the detection of the 

 presence of added vegetable colors in general, and recourse must there- 

 fore be had to the special tests for vegetable colors given below. The 

 presence of vegetable colors may be assumed if, after proving the 

 absence of coal-tar colors, the wine fails to come up to the tests for 

 pure wines, as given under this heading. In the absence of coal-tar 

 colors, and when by the preceding examination the presence of foreign 

 vegetable colors is indicated, the following procedure will be found 

 useful for indications of the character of the coloring matter present, 

 but in any case the presence and identity of the indicated color should 

 be proved by confirmato^ tests to be found in any of the text-books. 



Evaporate a sufficient quantity of the wine, depending upon the amount of color- 

 ing matter present, to small bulk, then make slightly acid with acetic acid, insert a 

 piece of wool previously mordanted with tin, and evaporate to dryness in a porcelain 

 dish. If the wool is dyed, remove it and wash thoroughly with water, note the color 

 it is dyed, and examine portions of the fiber according to the following table: 



Compt. rend., 1886, 102,52. 

 *>Bujard and Baier, Hilfsbuch., p. 295. 

 c Rottger, Lehrbuch der Nahrungs-Chemie, 1903, p. 478. 



d Fuchsin will be indicated by disappearance of the color on treating the wool 

 with ammonia. 



